1. Field of the Invention
The present invention relates to vehicle surroundings monitoring apparatus which extracts an object by binarizing an infrared image.
Priority is claimed on Japanese Patent Application No. 2004-175667, filed Jun. 14, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
Hitherto, there is a vehicle surroundings monitoring apparatus which extracts an object, such as a pedestrian which has a possibility of coming into collision with a vehicle, from an image of the vehicle's surroundings caught by an infrared image photographing device (an infrared camera). Specifically, in this apparatus, an infrared image is subjected to a binarization process to search the region where bright parts concentrate (a binarized object), and it is judged whether the infrared object is the head of the pedestrian or not, by calculating the aspect ratio, the demand fulfillment percentage of the binarized object, and further, the distance from an actual area and the centroid position in a display. When it is judged that the binarized object is the head of a pedestrian, height of the pedestrian in the image is calculated to determine the region which covers the body of the pedestrian, and these regions are displayed with assorting them from the other regions. In this way, it is possible to perform a visual assist more effectively, by specifying the position of whole body of a pedestrian in an infrared image and displaying this information to the driver of the vehicle, for example, as is disclosed in the patent document 1 (Japanese Unexamined Patent Application, First Publication No. H11-328364).
Moreover, in some vehicle surroundings monitoring apparatus, the pedestrian detection alarm is suppressed, when the weather of the surroundings of vehicles is rain and the pedestrian may hide in a rain gear, such as an umbrella. Specifically, in the case in which a pedestrian detection is performed using an infrared sensor, the detection accuracy may deteriorate because a pedestrian hides behind a rain gear such as an umbrella, thereby preventing the body temperature from being detected on a rainy day, in addition to the fact that the infrared sensor may detect the heat of asphalt and buildings. Therefore, it is proposed to stop outputting of the pedestrian detection alarm by detecting that the amount of rainfall is more than a predetermined amount, that is, such an amount that the pedestrian necessitates rain gear such as an umbrella and that the pedestrian may hide behind the rain gear, and informing the driver that the detecting accuracy of pedestrian deteriorates, for example, as is disclosed in the patent document 2 (Japanese Unexamined Patent Application, First Publication No. 2000-211453). Thereby, an unsuitable pedestrian detection alarm can be suppressed in the case in which the weather of the surroundings of vehicles is rain.
As mentioned above, comparative distinguishable physical features of a pedestrian who is present on a road, such as a pedestrian's head, cannot always be caught by an infrared camera. For example, as shown in FIG. 13 which shows an infrared image (gray scale image) which caught the pedestrian who used an umbrella, when the pedestrian holds an umbrella deeply (portion marked with a white circle in FIG. 13) such that the pedestrian's head is hidden, and there is a problem that recognition of the pedestrian may become difficult.
Therefore, in order to perform more effective visual assistance to a vehicle driver, it is necessary to improve the recognition percentage of a pedestrian by performing extraction of a pedestrian using not only comparative distinguishable physical features of a pedestrian such as judging based on stature, the head and the trunk of the body, and on the head only, as in the apparatus disclosed in the patent document 1, but also features other than the comparative distinguishable physical features of a pedestrian.
Moreover, even if the weather of the surroundings of a vehicle includes rain, when a pedestrian is present in the surroundings of the vehicle, it is still necessary to detect positively the pedestrian and to output an alarm so as to excite a vehicle driver's attention, unlike the apparatus disclosed in the patent document 2.